PROJECT SUMMARY The sirtuin enzyme SIRT6 promotes cellular homeostasis and organismal longevity through deacetylation of chromatin substrates around target promoters. The slow activity of the enzyme in vitro suggests that activators would be beneficial modulators of aging-related conditions. Despite this appeal, SIRT6 structure and function relationships are incompletely understood. This project seeks to determine unknown mechanisms of SIRT6 enzymology. Our finding that physical interactions with DNA and nucleosomes promote SIRT6 activity hints at novel mechanisms that regulate chromatin deacetylation. This study will tease out the mechanisms that drive this phenomenon, including shifts in enzyme conformation in different functional domains. The results will unveil how endogenous effectors induce sirtuin activity in the chromatin environment. Together, this project will reveal changes at the cellular and molecular levels that drive enzyme catalysis, leading to rational SIRT6 pharmacology.